Chapter 28: Enterprise Services

Overview

Chapter 23 explored the vast hinterland of legacy software known as COM. This chapter looks at “what COM did next” and how it fits into the world of .NET, in the form of .NET Enterprise Services. You would be forgiven for thinking that Enterprise Services is yet another version of legacy software, except that much of it hasn’t been around for long enough to be considered legacy. However, there is more to it than that. The features made available by Enterprise Services are still very valuable today for creating scalable, distributed applications.

To understand Enterprise Services, go back in time to around 1997 when a number of technologies began to emerge from Microsoft, including Microsoft Transaction Server (MTS), Microsoft Message Queuing (MSMQ), and Microsoft Clustering Services. The aim of these developments was to bring something that had previously been esoteric, specialized, and generally mainframe-based within the scope of standard PC technology, putting these technologies in the hands of developers.

Handling transactions involved a considerable extension to the NT/COM runtime. It also involved the introduction of several new standard COM interfaces, some to be used or implemented by transactional components and some to be used or implemented by the underlying resource managers, such as SQL Server. These additions, along with some other innovations relating to areas such as asynchronous COM, came to be known as COM +.

This chapter explores the .NET Enterprise Services. In particular, it looks at transaction processing and queued components using the classes of the System.EnterpriseServices and System .Transactions namespaces. This is an enormous subject that could easily fill a whole book by itself, so this chapter only scratches the surface of it. However, by the end of the chapter, you will understand how all the pieces fit together. Let’s begin by looking at what transactions are, and how they fit into Visual Basic 2005.

Important 

You can find more information about transactions in .NET in Professional VB.NET Transactions (Wiley, 2002).